If its just a stick on headlight tint then it should work, but you might get some reduced visibility from your headlights. That, and you might attract more attention from the local 5-0, I only say that cuz one of my friends had tint like this on his headlights and he took the tint off after a week due to getting pulled over so much.

I don't understand why people want to do this to their vehicles. I guess to achieve the "fully blacked out" look, but at what cost? The lights on your vehicle serve more than one purpose. Yeah, they allow you to see at night, but they also allow others to see you. Have you ever pulled out in front of someone in inclement weather, or at dawn or twilight? Someone you never saw because they're vehicle completely blended in with the road and the background and their lights were off? I have. Lots of people drive with their lights off early in the morning because they can see, not realizing how hard it is to see them in the low light. DRL help to resolve this somewhat, but many want to disable them also. I always drive with lights on, be it DRL or headlamps, regardless of the conditions outside. The better the chance of other drivers seeing you, the less chance of being involved in an accident.
I understand these things don't completely block out your headlights/tail lights, but I do know they can reduce the ouptut by a big amount. I used to work with a guy who had his blacked out all around, and at night you didn't know his tail lights were on and the brake lights were very dim. His headlights were also very diminished. I don't know if these things come in varying degrees (like tint), but I'm pretty sure his were not legal. I am very sure his were not safe, and wouldn't want them on my vehicle. Just something to consider.

Since you guys are on the legal issues of these things (which I agree with btw). There is also quite possibly an insurance ramification here too. If an accident occurs and the police determine that your diminished lights were the cause or partially to blame. Your insurance company might have a serious issue with you. As in trying to get out of paying or dropping you.

All that said the blacked out look is cool. As long as you can do it safely.

The last ones I saw worked. They hid the headlights nicely. For daytime driving they were cool. At night they killed the headlight output. Very dangerous. They were attached with Velcro and were removable. Problem is the owner was too lazy to take them off at night.